In the treatment of intracranial lesions with radiation, a number of practical difficulties exist in conventional procedures. In such treatments, it is necessary for the treatment beams to be accurately aimed in all treatment sessions in order to treat effectively with minimum adverse peripheral consequences. In order to insure accurate repeatability, it is necessary to positively fix the patient's head with respect to the radiotherapy machine and/or a CT scanner, and the mechanisms for accomplishing this have been unwieldy and require removal and reattachment from treatment session to treatment session. Because of limitations inherent in conventional procedures, it is difficult to effectively treat by radiotherapy extremely small intracranial lesions (i.e. smaller than 4.times.4 centimeters), although treatment of such lesions would be extremely advantageous in effecting total patient care.
According to the present invention a halo assembly is provided, for use with a stereotaxic device, which eliminates or minimizes most of the drawbacks associated with current devices and procedures. Utilizing the halo assembly, with stereotaxic device, according to the invention, a method of practicing radiotherapy on a patient having an intracranial lesion or the like is provided which is substantially more simplified and/or more accurate than conventional methods.
The preferred stereotaxic device with which the invention is utilized includes a frame having four radiolucent substantially planar walls arranged in a quadrate in plan view. Radiopaque indicia means are formed on each of the walls. The halo assembly comprises a conventional halo for treatment of cervical fractures, with means for operatively fixing the position of the halo assembly to the frame walls to positively position the halo assembly in a predetermined position with respect to the walls. Also, means are provided for fixing the frames with respect to a radiotherapy machine. Preferably the frame also includes a substantially planar base plate substantially perpendicular to the walls, and means defining a through passage in the base plate, interior of a volume defined by the walls, for receipt of the halo assembly. Fixation of the halo assembly to the frame is preferably accomplished utilizing a plurality of brackets, each bracket having a first portion affixed to the ring component of the halo assembly, and a second substantially planar portion extending radially outwardly from the ring component of the halo assembly, the second portions being substantially coplanar.
The invention also comprises a method of practicing radiotherapy (rotational or a fixed source) on a patient having an intracranial lesion or the like. The method comprises the following sequential steps: (a) Determining the approximate position of the intracranial lesion or the like in the patient's head. (b) Surgically affixing a halo assembly to the patient's head to be maintained in place until all radiotherapy sessions for the patient are completed, taking care to position the ring component of the halo assembly with respect to the patient's skull so that effective treatment with radiation will be practiced. (c) Positioning the halo assembly in, and fixing it to, a stereotaxic guide having radiopaque indicia associated therewith. (d) Fixing the stereotaxic guide in a CT scanner. (e) Operating the CT scanner to determine the exact position of the intracranial lesion or the like with respect to the indicia provided by the stereotaxic guide. (f) Transferring the patient to a radiotherapy machine. (g) Fixing the stereotaxic guide with respect to the radiotherapy machine. (h) Inputting the coordinates of the intracranial lesion or the like, determined from the CT scan, to the radiotherapy machine. (i) Operating the radiotherapy machine to provide one treatment session for the patient, positioned in the stereotaxic guide in the radiotherapy machine. (j) Removing the halo assembly from the stereotaxic guide. (k) Replacing the stereotaxic guide on the halo assembly when the patient returns for the next treatment session, the halo assembly remaining in place on the patient between treatment sessions. (l) Repeating steps (g) through (k) until all desired radiotherapy sessions for the patient are completed; and (m) removing the halo assembly from the patient's head.
Step (a) is preferably practiced utilizing a CT scanner. Also, as a further step (n) between steps (f) and (g), the patient is removed from the stereotaxic guide, and as further steps between steps (g) and (i), (o) proper position of the radiotherapy machine with respect to the intracranial lesion is tested utilizing a target device in the stereotaxic guide, and the relative position of the radiotherapy machine is adjusted if necessary; and (p) the halo assembly is fixed in the stereotaxic guide, and step (l) further comprises repeating steps (n) through (p) for each session.
It is the primary object of the present invention to provide for the simple and effective radiotherapy of patients having an intracranial lesion or the like. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.